Spark plug



Jan. 15, 1935- J. J. FERNANDEZ SPARK PLUG Filed Juge 15, 193s 5 4 w an?. J S

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Patented Jan. 15, 1935 UNITED sTATEs PATENT OFFICE SPARK PLUG John J. Fernandez, Baltimore, Md., assigner to Fernandes-Gibson Corporation, Washington, D. C., a corporation of Delaware Application June 15, 1933, Serial No. 875,988

8 Claims. (CL 12B-169) The invention relates to spark plugs for internal combustion engines and has for its object to provide a novel form of spark plug that is non-fouling, has a wide range o! adjustment of l the spark gap, is proof against burn outs and short circuits, operates at relatively low and substantially uniform temperatures with engines of various degrees o! compression and that serves to receive a small charge o! the explosive mixture to ignite the same-under comparatively low pressure and deliver a high velocity jet of name through a relatively small nozzle into the compressed explosive mixture in the engine cylinder, the size of the jet nozzle orice being inversely proportional to the degree oi compression under which the engine operates.

The invention is illustrated in the accompanying drawing, in whichz Fig. 1 is an elevation, on an enlarged scale, the improved spark plug.

Fig. 2 is a section on line 2-2 or Fig. 1. Referring to the drawing, 1 indicates the body or casing of the plug provided with the usual wrench engaging section 2 and having an upper chambered section 3 provided with an annular inclined shoulder constituting the seat for the usual core o! porcelain or other suitable insulating material, the upper interior portion of the cham- 80 bered section 3 being provided with screw threads 5.

Below the upper chamber 3 is an intermediate chamber 6, below which is a somewhat smaller chamber '1 terminating in a bottom wall 8, which is generally iiat and is provided with a central axial nipple 9, the bore of which constitutes an inlet to the chambers 6 and 'l and a :letting nozzle, as will be hereinafter explained. The lower peripheral portion o! the body is screw threaded as at 10 for securing the spark plug in place and at or about the lower limit of the screw threaded portion are diametrically disposed lateral openings ll, 11, the lower portions of which are substantially at the level of the ilat surface 8 constituting the bottom of the chamber '1,-said openings constituting sight openings for inspecting the spark gap and for the insertion of a gaugev to fix or determine the width of the spark gap, as will be hereinafter explained.

Mounted axially within the upper chamber 3 is the usual core 13 ot porcelain or other suitable insulating material, provided with an axial bore 14, the lower peripheral edge of the core having a coordinate bevel withthe beveled shoulder 4 o! the interior of the casing and adapted to bear under compression in the engine cylinder and upon a dished washer 15 of copper or the like. which effects a seal between the core and the casing. The upper reduced portion of the core is provided with a beveled shoulder with which eooperateswashers 16 and 16', which latter are 5 forced into sealing engagement with the core by a gland 17, which is in threaded engagement with the threads 5 on the interior of the upper chamber 3.

Fixed within the,axial bore -14 of the core 13 l0 is an electrode 20 in the form of a metallic rod having its upper end 21 screw threaded and extending beyond the end of the core, which screw threaded end is engaged by a nut 22 and a lock nut 24, which latter also constitutes a terminal lo connector for a circuit wire or conductor. One or more washers 23 are interposed between the nut 22 and the top ot the core and serve as means for sealing the bore 14 and also for adjusting the lower end oi the electrode and thereby determin- 20 ing the width oi the spark gap. Secured to an intermediate portion of the electrode is a shoulder or collar 25 and interposed between the latter and the base of the core is one or more washers or shims 26, which are interchangeable with 25 the washers 23 in the operation of adjusting` and regulating the width oi the spark gap. The lower end of the electrode 20 is provided with a disklike head 2'?, which, as shown, is frusto-conical in form and is preferably made of an alloy of iron 30 and copper in the proportions of 20% iron and 80% copper, which renders this terminal of the electrode non-fouling, non-corrosive and highly conductive of both heat and electricity. The bottom face of the head 2'1 is parallel with the 35 upper tace of the bottom wall 8 and the distance between said face and wall surface constitutes the spark gap, which is adjustable and is adjusted by applying or removing the washers or shims 26 between the shoulder. 25 and the lower 40 face of the core 13, the washers or shims being interchanged between the upper and outer end of the electrode on top of washer 23 and the shoulder or collar 25.

The width of a spark gapin any standard spark 45 plug should be accurately adjusted to accommodate the particular type of internal combustion engine with which the spark plug is employed.

In high compression engines,v a relatively narrow spark gap is essential to best results, for standard compression engines, a spark gap of somewhat greater width is desirable, while for low compression engines a spark gap oi.' established maximum width is desirable. While these varying widths of spark gaps have been recognized as necessary for xed in the end of the plug to produce the necessary width of the spark gap, which is determined by the usual nat metal gauge employed for this purpose. In cases in which the spark gap terminals are'relatively fixed and of a character such that either cannot be deformed to vary the width of the spark gap, it has been found necessary to manufacture plugs for each type of engine, depending upon the degree of compression under which it operates. The present invention provides a spark plug in which the spark gap may be properly adjusted for use in any of the various types of engines, the adjustment of the spark gap being eii'ected by applying or removing shims or washers, such as 26, between the shoulder 25 and the base of the core 13. For example, with a high compression engine requiring the minimum width of spark gap, three washers 26 are interposed between the shoulder 25 and the base of the core 13, which adjusts the lower face of the electrode terminal 27 the proper distance from the upper face of the bottom 'wall 8 of the plug. Should the plug be used with an engine operating under standard compression, one of the washers 26 would be removed and preferably applied to the upper end of the electrode 20 between the nut 22 and the sealing washer 23. If the plug is used with a low compression engine, two washers 26 would be removed and, for convenience, applied to the upper end of the electrode 20 between the nut 22 and the washer 23. 'Ihe removal of one washer 26 and the setting up of the electrode by the nut 22 will space the lower face of the electrode terminal 27 a proper distance from the bottom wall 8 to constitute a standard compression spark gap, while the corresponding removal of two washers 26 will commensurately increase the width of the spark gapagreeing with that required for best operation with standard compression engines. In order to accurately determine the width of the spark gap, an appropriate metal gauge may be inserted through the openings 11 in the lower portion of the spark plug casing and the shims 26 applied to or removed from position between shoulder 25 and the bottom of the core 13, as hereinbefore explained, until the proper spacing of the head 27 with respect to the bottom wall 8 is attained.

It has been found in actual practice that spark plugs made in accordance .with the foregoing description and illustration are non-fouling, prevent preignition of the explosive charge, show absolutely no tendency to burn out or to short circuit, do not become overheated but operate at a substantially uniform temperature in al1 types of engines, irrespective of the degree of compression employed.

In the regular operation of the plug, a small proportion ofthe explosive mixture, when the latter is undergoing compression, is forced through the nipple 9 into the chambers 6 and 7, but, owing to the restricted bore of the nipple, the portion of the explosive mixture in the chambers 6 and 7 is never under a compression more than 25% of the normal compression in the engine cylinder, so that the ignition spark will be propagated in an explosive mixture under relatively low compression, thereby materially increasing the efliciency of the ignition system and practically eliminating the possibility of misiire provided a spark passes between the terminal 27 and the bottom wall of the plug. The ignition of the low compression explosive mixture in the chambers 6 and 7 upon the passage of the spark between the terminal 27 and the wall 8 projects a jet of burning gases through the nozzle formed by the nipple 9 into the body of compressed gases in the engine cylinder and ignites the latter with certainty and dispatch. This jet or flame is not instantaneous like the jumping of the spark, but continues so long as the combustion of the explosive mixture in the chambers 6 and 'I maintains.

It has been found to be of considerable advantage to regulate the size of the bore of the nipple or jet nozzle 9 or the outlet end of said bore in consonance with the type of engine with which the spark plug is employed, as respects the compression under which the engine operates. For high compression engines, the size of the bore or the discharge end thereof should be of the order of one-eighth of an inch. When used with a low compression engine, the bore is preferably about three-sixteenths of an inch in diameter and for standard compression engines the size of the bore is between these two extremes. 'Ihe purpose of regulating the size of the bore of a jet nozzle is primarily to produce throttling to cut down the pressure of the explosive mixture entering the plug through said bore, so that the ultimate pres*- sure of the mixture inside the plug will approximate one-fourth the normal pressure in the engine cylinder at the end of the compression stroke of the piston. Obviously, if desired.`.instead of providing separate and distinct spark plugs for each type of engine, as distinguished by the size of the bores of the discharge nozzles, the plugs may be provided with separable and interchangeable nozzles having bores of different appropriate sizes to accommodate the plugs to the several types of engines. This may be effected by making the nipples 9 as separate elements screwed into the bottoms of the plugs, as will be understood by those skilled in the art.

- What I claim is:

1. A spark plug, comprising a shell having a chamber in its lower portion with a restricted jet nozzle in the bottom thereof and an electrode mounted axially in said shell and insulated therefrom and having a disk-like head on its lower end disposed at sparking distance from the bottom of the chamber.

2. A spark plug, comprising a shell having a chamber in its lower portion with a restricted jet nozzle in the bottom thereof, an insulating core secured in the upper portion of said shell, an electrode mounted axially in said core and having a disk-like head on its lower end disposed at sparking distance from the bottom of the chamber.

3. A spark plug as described in claim 2, in which the electrode is adjustable axially of the core to vary the width of the spark gap.

4. A spark plug as described in claim 2, in which the electrode is adjustable axially of the core to vary the width of the spark gap and the shell is provided with lateral openings adjacent the bottom thereof to permit gauging ofthe gap.

5. A spark plug, comprising an insulating portion and a shell portion the latter having a chamber in its lower portion said chamber being provided with a restricted and elongated jet nozzle in the bottom thereof, an electrode mounted in said insulating portion and extending axially of both portions said electrode having an enlarged head at its lower extremity said head being disposed at sparking distance from the adjacent walls of the said chamber.

6. A spark plug comprising an insulating portion, a shell portion and an electrode, said shell portion having a chamber which is provided at its lower end with a restricted and elongated jet nozzle, said electrode extending through said insulating portion and terminating at sparking distance from the wall or said chamber adiacent said jet nozzle.

JOHN J. FERNANDEZ. 

